Bird Song and the Problem of Honest Communication

People can be tempted to be dishonest with one another: to exaggerate our income to someone we're dating, for example, or, conversely, to understate our income to the Internal Revenue Service. Although morality does play a role in the degree of truth imparted in the messages that we actually deliver, we also use a rational calculation of costs and benefits to decide whether to dissemble. But when animals communicate, we don't necessarily expect individuals to make decisions based on either moral standards or societal rules. Rather, we expect the rules determining the honesty of a signal to be imposed by natural selection, with costs and benefits ultimately measured in terms of relative reproductive success. How natural selection works to keep animal signals reliable, and the nature of the outcome, is currently a central question in animal behavior. Bird song provides an excellent model for exploring the mechanisms that keep animals honest as they pursue mates or defend their territory, and may ultimately help us to understand how communication, including our own, has evolved.